From the 14th to the 16th centuries, the Kingdom of Ryukyu engaged in a prosperous overseas trade with China, Korea, and
Southeast Asia. The overseas trades with various nations formed a foundation for Okinawa's unique and diverse culture. The
unique culture of the Ryukyus may well be symbolized by the stone structure of Gusuku (castles and their ruins) in various parts of Okinawa.

Gusuku in Okinawa represents a highly sophisticated technique using stones for various structures including the walls of the castles. Gusuku sites also provide a place for the people of Okinawa to worship their gods. Utaki worship is a unique religion that has been passed down from generation to generation.Utaki is a sacred place including the place known to be the beginning of the history of Okinawa, and natural objects are worshipped. During the period of the Kingdom of Ryukyu, Sonohyan-utaki and Sefa-utaki were recognized as the sacred places where the kingdom's religious rituals were performed.

Gusuku sites and the related properties of the Kingdom of Ryukyu were designated as World Heritage sites since they represent
unique and international culture of the kingdom that enjoyed a prosperous overseas trade and a unique religious form of the local areas of Okinawa that is characterized by nature worship.